Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)The behavior of model systems formed by different concentration of sodium caseinate and locust bean gum (LBG) was investigated using confocal microscopy (CSLM) and theological measurements in order to determine the interaction between these two ingredients in acidified dairy products. A visual phase diagram was constructed at different biopolymer concentrations and four different types of systems were observed for the mixtures in the isoelectric point of protein: one-phase gels (G1P), two-phase gets (G2P), one-phase liquid mixtures (L1P) and two-phase liquid mixtures (L2P). These different systems resulted from the different kinetics of phase separation and gel formation. The one-phase systems (gels and liquid mixtures) showed a micro-phase separation when visualized by CSLM, although they were homogeneous at macroscopic level. In a general way, the micro or macro phase separation led to a biopolymer concentration on separated phases, resulting in an increase of the stress at fracture for the gels or the viscosity for the liquid mixtures. However, the behavior of the whole system did not correspond to the sum of the mechanical properties of separated phases. (C) 2009 Elsevier Ltd. All rights reserved.23820852093Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)FAPESP [2003/00578-0, 2004/08517-3]CNPq [301869/2006-5]